In multicast and broadcast applications, data are transmitted from a server to multiple receivers over wired and/or wireless networks. A multicast system as used herein is a system in which a server transmits the same data to multiple receivers simultaneously, where the multiple receivers form a subset of all the receivers up to and including all of the receivers. A broadcast system is a system in which a server transmits the same data to all of the receivers simultaneously. That is, a multicast system by definition can include a broadcast system.
Wireless networks, given their low deployment cost and flexibility, have increasingly been used as the last hop extension of wired networks. Emerging technologies such as Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-In-Multiple-Out (MIMO) have effectively significantly increased the bandwidth of a wireless channel. A potential application of these technologies is to distribute video content over wireless links in a home environment. Distribution of video content such as by video streaming is bandwidth demanding. In most homes, a one hop wireless local area network (WLAN) is sufficient for network access. When a playback device (TV or computer) is far away from a access point (AP) and/or gateway, a multi-hop wireless network may be necessary for a certain level (quality) of viewing experience. A multi-hop wireless network uses a routing protocol to select the best path (route) from a source to destination. Some protocols such as Automatic On-demand Distance Vector (AODV) find the shortest path (route). An earlier filed application PCT/US05/039597 filed Nov. 2, 2005 extended AODV to take bandwidth into consideration. In some cases, when there are one or more interfering wireless devices, even the best route cannot provide enough bandwidth for video distribution, switching to a less interfering channel may solve the problem.
A great deal of study has been devoted to combining packet scheduling, routing and channel selection to support multi-radio and multi-channel wireless ad-hoc or mesh networks, such as Kyasanur and Vaidya, “Routing and Link-layer Protocols for Multi-Channel Multi-Interface Ad Hoc Wireless Networks,” SIGMOBILE Mobile Computing and Communication Review, vol. 10, no. 1, pp. 31-43, January 2006; Alicherry et al “Joint Channel Assignment and Routing for Throughput Optimization in Multi-radio Wireless Mesh Networks,” in ACM Mobicom, Cologne, Germany, August 2005; Bahl et al. “SSCH:Slotted Seeded Channel Hopping for Capacity Improvement in IEEE 802.11 Ad-Hoc Wireless Networks,” In Proceedings of ACM Mobicom, Philadelphia, Pa., September 2004. These studies, however, propose modifications to the current IEEE 802.11 MAC layer, and assume that all the devices in the wireless network are synchronized and that channel switching can be performed on a per packet basis. In “Centralized Algorithms for Multi-channel Wireless Mesh networks,” in ACM Mobile Computing and Communication Review, April 2004, Raniwala et. al proposed a scheme for relatively long term channel assignment for a multi-radio mesh network, the goal was to increase the total capacity of a mesh work. Raniwala et. al does not combine routing with the channel assignment protocol. Other proposals, such as Nelson and Kleinrock, “Spatial TDMA: A Collision Free Multihop Channel Access Protocol,” IEEE transactions on communications, vol. com-33, No. 9, pp. 934-944, September 1985 and Cidon, Moshe Sidi, “Distributed Assignment Algorithms for Multihop Packet Radio Networks,” IEEE transactions on computer, vol. 38, no. 10, pp. 1353-1361, October, 1989 advocate the use of TDMA MAC layer to increase the spatial reuse of wireless channels. These proposals, again, require modification of the IEEE 802.11 MAC layer. In an earlier filed application PCT/US05/039597 filed Nov. 2, 2005, a bandwidth aware routing protocol was proposed, which selected a path that had the best bandwidth instead of the shortest hop. This was better for video streaming, which is bandwidth demanding. However, when there are one or more interfering devices in the neighborhood, even this protocol may still fail to find a path that can meet the requirements of a video streaming, In the case of an interfering channel, switching to a less interfering channel may solve the problem.
Bandwidth aware routing protocol needs information about available bandwidth between a node and its neighbors in a wireless network. The available bandwidth maybe estimated using information from IEEE 802.11k, but currently IEEE 802.11k is not implemented in most of the wireless cards. In Shah et al “Available Bandwidth Estimation in IEEE 802.11-based Wireless Networks,” In Proceedings of 1st ISMA/CAIDA workshop on Bandwidth Estimation (BEst 2003), a MAC layer available bandwidth estimation method was proposed. In an Ad-hoc or mesh wireless network, each node may have multiple neighbors. The method in Shah et al requires the MAC layer to maintain neighboring nodes status.
A method that combines bandwidth aware routing and channel selection for video distribution in a multi-hop wireless home network would be useful. New application layer methods to estimate available bandwidth between neighboring nodes in a wireless network that do not require maintaining the status of neighboring nodes would also be useful.